1. Field of the Invention
This invention relates to a cooling unit including an evaporator therein, and more particularly, to a cooling unit suitable for use in an automotive air conditioning system.
2. Description of the Prior Art
Referring to FIG. 1, a refrigerating circuit of an automotive air conditioning system in accordance with one embodiment of the prior art is shown. Refrigerating circuit 10 includes compressor 11, condenser 12, receiver-dryer 13, expansion valve 14, evaporator 15 and silencer 16, all of which are interconnected through conduit 17. In refrigerating circuit 10, refrigerant gas is compressed by compressor 11. Compressed refrigerant gas flows to condenser 12 and is condensed therein by heat exchange. Condensed refrigerant flows to expansion valve 14 via receiver-dryer 13 and is expanded thereby. Expanded refrigerant then flows to evaporator 15 and is vaporized therein by heat exchange. Vaporized refrigerant returns to compressor 11 via silencer 16. Silencer 16 levels the pulsation of refrigerant flow due to refrigerant being sucked into compressor 11 through valved ports (not shown). The pulsation of the refrigerant flow causes casing 21 of evaporator 15 to vibrate, thereby producing an offensive noise in the automotive passenger compartment.
With reference to FIGS. 2 and 3, a cooling unit in accordance with one embodiment of the prior art is shown. Cooling unit 20 includes evaporator 15 housed in casing 21 having air inlet and air outlet openings 211 and 212. Heat insulating member 22, made of foamed polystyrene, lines an inner surface of casing 21. Evaporator 15 is air-tightly disposed within casing 21 through heat insulating member 22. During operation, an evaporator motor fan (not shown) forces air through evaporator 15 via air inlet and outlet openings 211, 212 as indicated by arrows 23, 24. The refrigerant in evaporator 15 absorbs heat from the air passing therethrough as the heat of evaporation.
In the prior art, the offensive noise produced in the automotive passenger compartment due to the pulsation of refrigerant flow is reduced or eliminated by disposing silencer 16 between evaporator 15 and compressor 11. However, the addition of silencer 16 into the automotive air conditioning system increases component part, inventory and assembly costs.